For better app performance, some of the XML classes in the .NET Framework support a streaming-based model with the following characteristics:

Minimal caching for forward-only, pull-model parsing (XmlReader).

Forward-only validation (XmlReader).

Cursor style navigation that minimizes node creation to a single virtual node while providing random access to the document (XPathNavigator).

For better performance whenever XSLT processing is required, you can use the XPathDocument class, which is an optimized, read-only store for XPath queries designed to work efficiently with the XslCompiledTransform class.